响应面法优化红柳枝烟熏液制备工艺及其理化特性分析

以红柳枝为实验材料，在高温下干馏（厌氧热解）得到烟熏液，通过单因素试验和响应面设计法，研究干馏温度、干馏时间和木材厚度对红柳枝烟熏液产率、酚含量、羰基化合物含量的影响，进而确定红柳枝烟熏液制备工艺参数的最优组合。在最佳制备工艺参数的基础上，探究干馏温度对红柳枝烟熏液色泽的影响和吸附精制处理对红柳枝烟熏液理化性质的影响。结果表明：最优参数组合为干馏温度402.22 ℃、干馏时间75.66 min、木材厚度0.627 cm，该条件下制备烟熏液的酚含量为10.066 mg/mL、羰基化合物含量为14.35 g/100 mL、烟熏液产率为33.082%；烟熏液的亮度值（L*）随干馏温度的增大而降低，黄度值（b*）、色度值和色调随干馏温度的增大变化趋势与L*相似，但红度值（a*）的变化趋势与L*相反（P＜0.05），随干馏温度的升高，红柳枝烟熏液总色泽的变化趋势由淡黄色至棕褐色，当干馏温度为380 ℃时，总色差（ΔE）最小，红柳枝烟熏液的色泽鲜艳、与商业烟熏液最接近；大孔树脂与核桃壳吸附精制对烟熏液pH值没有影响，但降低苯并(a)芘含量、酚含量、羰基化合物含量和烟熏液产率（P＜0.05），苯并(a)芘含量远低于国标限量（0.5 μg/kg）。

Liquid Smoke from Red Willow Twigs: Optimization of Preparation Process by Response Surface Methodology and Physicochemical Analysis

Liquid smoke was prepared by dry distillation (anaerobic pyrolysis) of red willow twigs. The effects of dry distillation temperature, dry distillation time and wood thickness on the yield, phenol content and carbonyl compound content of liquid smoke were investigated by the combined use of one-factor-at-a-time method and response surface methodology (RSM). Based on the obtained results, the optimal combination of processing parameters was determined. Further, the effect of retorting temperature on the color of the liquid smoke prepared with the optimized processing conditions was evaluated along with the effect of adsorption-based refining on its physicochemical properties. Dry distillation at 402.22 ℃ for 75.66 min and a wood thickness of 0.627 cm were found to be the optimal conditions. Under these conditions, the yield of liquid smoke was 33.082%. The contents of phenolics and carbonyl compounds in the obtained product were 10.066 mg/mL and 14.35 g/100 mL, respectively. The experimental values were consistent with the predicted ones. The lightness value (L*) of liquid smoke declined with increasing retorting temperature, and so did the yellowness value (b*), chromaticity value and hue. However, the opposite trend was observed for the redness value (a*) (P < 0.05). As retorting temperature rose, the liquid smoke changed from yellowish to brown, and the lowest total color difference (ΔE) was observed at a retorting temperature of 380 ℃. The bright color of the product prepared under this condition was the closest to that of a commercial one. Refining by adsorption onto macroporous resin and walnut shells had no impact on the pH value of liquid smoke despite reducing the contents of benzo(a)pyrene, phenolics and carbonyl compounds in liquid smoke and its yield (P < 0.05). The content of benzo(a)pyrene in the liquid smoke prepared in this study was far below the Chinese national standard limit (0.5 μg/kg).